In recent years, expectation for a magnetoresistive random access memory (MRAM) as a memory having non-volatile characteristics and achieving high speed, high integration, low power consumption, and high reliability has been increased. A basic element of the MRAM has a structure called magnetic tunnel junction (MTJ) in which an insulating film used for tunnel barrier is interposed between two ferromagnetic layers. The information is recorded by using tunnel magneto-resistance (TMR) effect that a resistance of the element is significantly different depending on either a parallel direction or a non-parallel direction in magnetization of these two ferromagnetic layers. More particularly, by a (spin-injection magnetization reversal type) method of rewriting the magnetization direction by bi-directionally carrying a current in the TMR element so as to inject spin-polarized electrons which are different depending on the magnetization of the ferromagnetic layers, a writing current can be reduced in accordance with microfabrication, so that the high integration and the low power consumption are possible in accordance with scaling of a semiconductor device. Also in such a memory, a multi-value technique capable of storing a lot of information in one memory cell has been studied for achieving a low bit cost.
Here, Patent Document 1 describes a magnetic memory in which the multi-value technique is achieved by connecting a plurality of TMR elements in series to each other. Also, Patent Document 2 and Patent Document 3 describe a magnetic memory in which a storage element of a memory cell is formed by arranging a plurality of TMR elements in parallel to each other with using a spin-injection magnetization reversal element.